One device that has become generally accepted and is commonly used by physicians and other health care professionals is known as a radiation thermometer, or infrared thermometer. Such devices are commercially available from Thermoscan, Inc. of San Diego, Calif. Devices of this type are described, for example, in U.S. Pat. Nos. 5,368,038 (Fraden), 4,797,840 (Fraden), 4,479,931 (Mooradian), 5,127,742 (Fraden), 5,178,464 (Fraden), 5,626,147 (Lackey), 4,895,164 (Wood), and 5,199,436 (Pompei). A radiation thermometer noninvasively detects thermal radiation from the tympanic membrane in order to determine the body temperature of the patient. A temperature reading made with this device may vary depending on the angle and depth of placement of the tip of the device with respect to the ear canal. In particular, the geometric relationship between the sensor and the tympanic membrane influences the ultimate reading by the sensor in operation. The field of view of the device when detecting thermal radiation also affects the temperature reading. The technology described in U.S. Pat. No. 5,626,147 (Lackey) seeks to solve these problems by using a sensor geometry which has wide and narrow fields of view and a look-up table with corrective values to provide an output indicative of the body temperature.
Another device that is used for diagnosis of ear pathologies is known as an acoustic reflectometer. Such devices are commercially available from MDI Instruments, Inc. of Woburn, Mass. under the trademarks "EARCHECK" and "EARCHECK PRO." Devices of this type are described, for example, in U.S. Pat. Nos. 4,601,295 (Teele), 4,459,966 (Teele), and 5,699,809 (Combs et al.), all of which are assigned to MDI Instruments, Inc. U.S. Pat. Nos. 5,594,174 (Keefe) and 5,651,371 (Keefe) also describe a device for measuring acoustic reflectance in a manner that permits the incident and reflected acoustic signals to be separately measured. An acoustic reflectometer measures sound waves emitted from the ear in response to a stimulus applied to the ear. The measured reflectance may be analyzed to determine the likelihood that fluid is present in the middle ear. Without correction or appropriate signal analysis, measurements made using an acoustic reflectometer also may be affected by line of sight from the tip of the device to the tympanic membrane. Although U.S. Pat. No. 5,699,809 (Combs et al.) describes a device in which the output is substantially independent of the line of sight, the device primarily determines the likelihood that fluid is present in the ear. However, in the detection of acute otitis media (AOM), otitis media with effusion (OME) or severe ear infection, the presence of fluid is only one factor in a diagnosis.